There is a marriage for Catharine Anne Marendaz in FreeBMD June 1849 Neath RD vol 26 Page 773, but there is no Townsend on this page:
Marriages Jun 1849
Davies David Neath 26773
Grier Eliza Neath 26773
Hanbury Sarah Neath 26773
Isaac Richard Neath 26773
Jones Ann Neath 26773
Llewellyn Catharine Neath 26773
Marendaz Catharine Ann Neath 26773
Phillip David Neath 26773
Phillips David Neath 26773
Williams Morgan Neath 26773
Also on page 772a:
Marriages Jun 1849
David Evan Neath 26772a
Evans Ann Neath 26772A
Lewis Margaret Neath 26772A
Marendaz Catharine Ann Neath 26772a
Thomas John Neath 26772a
In fact, looking at the image for Townsend on Ancestry, one sees that there is an entry at Neath, but it has been added between lines:
Townsend Edward Thomas Neath Vol XXVI page not clear (772?)
Cambrian Newspaper, Swansea:
Cambrian B10 MARRIAGES, MARRIAGE 08 June 1849 N.T.TOWNSEND,BRIDGEND TO CATHERINE MARENDEZ, TYDRAW,ABERAFON. AT MARGAM CHURCH.